1. Field of the Invention
The present invention relates to an insulating sheet having good adhesiveness and heat conductivity and a method of producing it, and to a power module including the insulating sheet.
2. Description of the Related Art
Heretofore, a heat-conductive sheet is used as a heat conductor, attached to a heat generator of electric and electronic parts for transferring and radiating the heat from the heat generator to a heat sink member. For it, for example, there is known a laminate of a metal sheet of copper, aluminium or the like or a graphite sheet having a heat conductivity of at least 10 W/mK, with an adhesive layer containing a heat-conductive filler and capable of adhering at room temperature laminated on at least one surface of the sheet (for example, see JP-A-2002-194306 (page 1)).
However, since the above-mentioned heat-conductive sheet includes plural layers of a sheet material such as a metal sheet or a graphite sheet and an adhesive layer, there exists an interface of a metal or graphite surface and an organic component of the adhesive layer between the sheet material and the adhesive layer therein, and the adhesiveness of the heat-conductive sheet is low in and around the interface area. Therefore, the heat-conductive sheet of the type is problematic in that both the heat conductivity and the insulating property thereof are poor.